A leaf/spine network utilizes Equal-Cost Multi-Path (ECMP) routing to spread all flows across multiple network paths. This is typically done by hashing packet headers to choose an output link. The hash is not aware of the bandwidth of a flow (i.e., it does not differentiate between mice and elephant flows), so it distributes flows evenly across links the way Link Aggregation Group (LAG) would. As implied by the names, an elephant flow is an extremely large continuous flow over a network link while a mice flow is a small size flow. A hash might spread flows evenly across many paths, but it can put two elephant flows on one link thereby creating a hotspot of congestion, which leads to packet drops and requires a management system to re-balance the whole network. But even after re-balancing, the elephant flows can lead to poor overall utilization of available path bandwidth. It is therefore desirable to avoid the creation of elephant flows.
OTN transport (i.e., Time Division Multiplexing (TDM)) is typically performed over dedicated OTN networks. In the context of transporting OTN over a packet network, i.e., encapsulation, the conventional approach includes OTN Over Packet Fabric Protocol (OFP) which is an Implementation Agreement from the OIF (IA # OIF-OFP-01.0), November 2011, the contents of which are incorporated by reference herein. Also, pseudo-wires can also be used. OFP and pseudo-wires provide circuit emulation. However, these conventional approaches encapsulate an entire Optical Data Unit 4 (ODU4) into a single elephant packet flow which causes the issues described above.